If |m|<1, then the line's inclination to
axis x is smaller than 45 grades, therefore the line is patterned
according to axis x with a step of 1 pixel. If |m|>1,
then it is patterned according to axis y. A line with slope 1 is
called diagonal and it is patterned by any axis. The axis according to
which it is patterned is called operative (main) axis. The name of second
axis is incident axis.